Microtech ® Iii Unit Controller - Daikin Enfinity VFC Installation And Maintenance Manual

MicroTech III Unit Controller
®
The MicroTech III Unit Controller includes built-in
features such as random start, compressor time delay,
shutdown, condensate overflow protection, defrost cycle,
brownout, and LED/fault outputs. Refer to Table 10 on
page 14 .
The unit has been designed for operation with a
microelectronic wall thermostat selected by the
manufacturer. Do not operate the unit with any other
type of wall thermostat.
Each unit has a printed circuit board control system. The
low voltage output from the low voltage terminal strip
is AC voltage to the wall thermostat. R is A/C voltage
output to the wall stat.
The 24 volt low voltage terminal strip is set up so R-G
energizes the fan, R-Y1 energizes the compressor for
cooling operation, R-W1 energizes the compressor and
reversing valve for heating operation. The reversing valve
is energized in the heating mode. The circuit board has
a fan interlock circuit to energize the fan whenever the
compressor is on if the thermostat logic fails to do so.
The output to the wall stat is AC current. Terminal (R) on
the wall stat can be connected to terminal (R) on the PC
board for AC voltage.
R = AC current
R to Y1 = cooling R to W1 = heat
The MicroTech III unit controller has a lockout circuit
to stop compressor operation if any one of its safety
switches opens (high pressure switch and low pressure
switch on unit sizes 024 through 060). If compressor low
suction temperature is detected, the unit will go into the
cooling mode for 60 seconds to defrost any slush in the
water-to-refrigerant heat exchanger. If the condensate
sensor detects a filled drain pan, the compressor
operation will be suspended only in the cooling mode.
The unit is reset by opening and closing the disconnect
switch on the main power supply to the unit in the event
the unit compressor operation has been suspended due
to low temperature (freezestat) switch, high pressure
switch, or low pressure switch on unit sizes 048 thru
060. The unit does not have to be reset on a condensate
overflow detection.
The MicroTech III unit controller fault output sends a
signal to an LED on a wall thermostat. Table 9 on page
13 shows for which functions the fault output is "on"
(sending a signal to the LED), when the "A" terminal is
configured by JP4 being open.
IM 930-6 • Enfinity Vertical Water Source Heat Pumps
R to G = fan only
Remote Reset of Automatic Lockouts
The Remote Reset feature provides the means to
remotely reset some lockouts generated by high-pressure
and/or low-temperature faults. When the MicroTech III unit
controller is locked out due to one of these faults, and the
cause of the fault condition has been cleared, energizing
the O-terminal for 11 seconds or more forces the
MicroTech III unit controller to clear the lockout. Cycling
unit power also clears a lockout if the conditions causing
the fault have been alleviated.
The Intelligent Alarm Reset feature helps to minimize
nuisance trips of automatic reset lockouts caused by low
temperature faults. This feature clears faults the first two
times they occur within a 24-hour period and triggers
an automatic lockout on the 3rd fault. The retry count is
reset to zero every 24 hours.
The MicroTech III unit controller has built-in night
setback operation. A "grounded' signal to the "U"
terminal on TB3 of the unit control puts the unit into
the unoccupied mode for night setback operation. Fan
operation terminates and unit control will only respond to
signal at the W2 terminal. Daytime heating and cooling
operation is locked out. +24VAC to W2 energizes the
compressor and reversing valve for heating operation.
Night setback operation can be overridden for two
hours by energizing the O on the TB2 terminal of
the unit control for 4 to 10 seconds. Day thermostat
setpoints then control the heating and cooling operation.
The MicroTech III unit controller also accommodates
shutdown operation on receipt of a "grounded" signal to
the "E" input, respectively, on TB3 input terminal of the
unit control .
The IV/PR(H8) terminals of the MicroTech III unit
controller are used for motorized valve / pump restart.
This terminal passes a voltage signal whenever the
unit compressor is turned on. This signal is detected
by a pump restart relay providing a N.O. or N.C. set
of contacts for heat pump loop circulation pump or
motorized valve control. When used with a system
control (by others), the relay operation accommodates
turning off circulation pumps during unoccupied periods
with a safety override dependent, at minimum, on
WSHP's need. The IV/PR(H8) terminals may be "daisy
chained" between 200 units.
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ontrols
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